Device to device communication method and apparatus

ABSTRACT

Embodiments of the present invention provide a device to device D2D communication method and apparatus, to resolve at least a problem of a low success rate of discovery between user equipments in the prior art. The method includes: determining, by first user equipment UE, to-be-sent first signaling, where the first signaling includes one or a combination of the following information: a transmission probability, a quantity of retransmission times, a transmission period, a type of a cyclic prefix CP, a transmit power, a current quantity of hops, a quantity of antenna ports, a transmission mode, a bandwidth of a D2D link, a D2D link frame number, time division duplexing TDD uplink and downlink configuration information, or information indicating whether the first UE is within a network; and sending, by the first UE, the first signaling to second UE by using the D2D link.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/707,420, filed on Sep. 18, 2017, which is a continuation ofInternational Application No. PCT/CN2015/074630, filed on Mar. 19, 2015.All of the afore-mentioned patent applications are hereby incorporatedby reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to the field of wireless communications,and in particular, to a device to device (D2D) communication method andapparatus.

BACKGROUND

With continuous development of wireless communications systemtechnologies, to implement communication, a D2D communication mode, inaddition to a conventional cellular communication mode, may also beused. In the cellular mode, a user equipment (UE) communicates withanother UE by using a base station. In the D2D communication mode, UEdirectly communicates with another UE. For a UE, D2D communication notonly saves radio resources and spectrum resources but also lowers apressure of a core network. Therefore, a D2D technology becomes animportant technology that can face the Fifth Generation (5G) and that isbeing currently standardized in the Third Generation Partnership Project(3GPP) standard.

In the D2D communication mode, one technology is device discovery.Device discovery refers to a process in which devices participating inD2D communication determine mutual existence before transmitting D2Dinformation. In the prior art, devices participating in D2Dcommunication implement device discovery under scheduling by a corenetwork device. The core network device herein may be a base station ina cellular communications network or a similar device.

However, in some scenarios in which D2D communication is frequentlyapplied, for example, when devices participating in D2D communicationare at a position, such as a basement or an elevator hatchway, at whichthe devices cannot establish a wireless connection to a core networkdevice, or at a position at which the devices establish an unstablewireless connection to a core network device, the devices participatingin D2D communication have a low success probability when performingdevice discovery, and consequently D2D communication is affected.

SUMMARY

Embodiments of the present disclosure provide a device to device D2Dcommunication method and apparatus, to resolve at least a problem of alow success rate of discovery between user equipments in the prior art.

According to an aspect, an embodiment of the present disclosure providesa device to device D2D communication method. The method includes thefollowing steps.

First user equipment (UE) determines to-be-sent first signaling. Thefirst signaling includes one or a combination of the followinginformation: a transmission probability, a quantity of retransmissiontimes, a transmission period, a type of a cyclic prefix (CP), a transmitpower, a current quantity of hops, a quantity of antenna ports, atransmission mode, a bandwidth of a D2D link, a D2D link frame number,time division duplexing TDD uplink and downlink configurationinformation, or information indicating whether the first UE is within anetwork. The first UE sends the first signaling to second UE by usingthe D2D link.

In a possible design, the first UE may determine the first signaling byitself according to a predetermined rule. In another design, the firstUE may also receive first signaling that is sent by third UE by usingthe D2D link and determine the to-be-sent first signaling according tothe first signaling sent by the third UE. The to-be-sent first signalingdetermined by the first UE and the first signaling sent by the third UEmay be the same or different in formats or content. In another design, abase station may configure first signaling for the first UE and send theconfigured first signaling to the first UE. The first UE receives thefirst signaling sent by the base station and determines the to-be-sentfirst signaling according to the first signaling sent by the basestation. The to-be-sent first signaling determined by the first UE andthe first signaling configured by the base station may be the same ordifferent in formats or content.

In a possible design, after the first UE receives the first signalingthat is sent by the third UE by using the D2D link, the first UE mayreceive or send data according to the first signaling sent by the thirdUE.

In a possible design, first information of at least one piece ofinformation included in the first signaling is further used toimplicitly indicate second information of the at least one piece ofinformation included in the first signaling. For example, informationthat may be included in the to-be-sent first signaling determined by thefirst UE has an association relationship. The first UE may carry a partof the information in the to-be-sent first signaling. The second UEreceives the part of the information sent by the first UE, and may know,according to the association relationship, other information associatedwith the part of the information. By means of such a design, resourcesoccupied by the first signaling may be saved.

In a possible design, the first UE may transmit a D2D synchronizationsignal in the D2D link. Optionally, the D2D synchronization signalincludes a primary sidelink synchronization signal PSSS and a secondarysidelink synchronization signal SSSS, sidelink synchronization signalidentities SLSSIDs that correspond to the PSSS and the SSSS are integersnot less than 336, and the SLSSIDs are used to identify a channelcarrying the first signaling in the D2D link.

In a possible design, the first UE sends the first signaling to thesecond UE by using a dedicated control channel or a non-control channelin the D2D link. For example, a reserved field included in the dedicatedcontrol channel may be used, and some or all bits in the reserved fieldare used to carry the first signaling.

In a possible design, the dedicated control channel may further carrysecond signaling, and the second signaling is used to identify that thededicated control channel is a channel carrying the first signaling.

In another possible design, the dedicated control channel may carry ademodulation reference signal DMRS, the DMRS is used to identify thatthe dedicated control channel is a channel carrying the first signaling,and a generation parameter u corresponding to the DMRS satisfies:u=(f_(gh)(n_(s))+f_(ss)) mod 30+b, where n_(s) is a non-negative integerand represents a timeslot number or a subframe number, f_(gh)(n_(s)) isan integer and represents a sequence group hop, f_(ss) is an integer andrepresents a sequence hop, mod represents a modulo operation, and b is anon-zero integer. Preferably, f_(ss) satisfies: f_(ss) ((SLSSID mod30)+Δ) mod 30, where SLSSID is an integer not less than 0, and Δ is anon-zero constant.

In a possible design, the dedicated control channel is scrambled byusing a scrambling sequence when being generated, the scramblingsequence is used to identify that the dedicated control channel is achannel carrying the first signaling, and an initial value c_(init) usedwhen the scrambling sequence is generated satisfies: c_(init)=nSLSSID orc_(init)=n_(RNTI)*2¹⁴+q*2¹³+└n_(s)/2┘*2⁹+SLSSID, where n_(RNTI), q, andn_(s) are all non-zero integers, SLSSID is an integer not less than 0,and nSLSSID is an integer not less than 336.

In a possible design, the dedicated control channel uses a cyclicredundancy check CRC mask when being generated, and the CRC mask is usedto identify that the dedicated control channel is a channel carrying thefirst signaling.

In a possible design, the first signaling sent by the first UE to thesecond UE is carried in one or a combination of the following manners: aCRC mask, a D2D synchronization signal, or a DMRS.

When the first signaling is carried by the D2D synchronization signal,different sequences of the D2D synchronization signal are divided into Msubgroups, and the M subgroups are used to carry information notexceeding n=floor(log₂(M) bits, where a floor function representsrounding down to the nearest integer.

When the first signaling is carried by the DMRS, the first signaling iscarried by modulation symbols on two neighboring DMRSs in the D2D link;the first signaling is carried by a modulation symbol on either of twoneighboring DMRSs in the D2D link; or the first signaling is carried bycyclic shifts of different DMRSs in the D2D link.

In a possible design, if the first UE is in-network UE, the first UEsatisfies at least one of a condition A or a condition B: the conditionA: quality of a signal that is received by the first UE and that is fromthe base station is less than a first threshold; and the condition B:quality of a signal that is received by the first UE and that is fromout-of-network D2D UE is greater than a second threshold.

If the first UE is out-of-network UE, the first UE satisfies a conditionC: quality of a signal that is received by the first UE and that is fromanother UE is less than a third threshold.

According to another aspect, an embodiment of the present disclosurefurther provides a user equipment (UE), including corresponding modulesconfigured to perform behaviors of the first UE in the foregoing methoddesigns. The modules may be software and/or hardware.

In a possible design, the user equipment (UE) includes a processor and amemory. The processor is configured to support the UE to performcorresponding functions in the foregoing method. The memory isconfigured to be coupled to the processor and stores necessary programinstructions and data of the UE.

According to still another aspect, an embodiment of the presentdisclosure further provides a communications system. The system includesthe first UE and the second UE in the foregoing aspects. The system mayalso include the third UE or the base station in the foregoing aspects.

According to yet another aspect, an embodiment of the present disclosureprovides a computer storage medium, configured to include programsinvolved in performing the foregoing aspects.

Based on the D2D communication method, the user equipment, and thesystem that are provided in the embodiments of the present disclosure,on one hand, a D2D device (first UE) sends first signaling to anotherD2D device (second UE) by using a D2D link, so that different D2Ddevices can receive and transmit data by using same parameters in a sameresource pool (a set of user resources) when sending a D2D discoverysignal, so as to implement D2D discovery between partially covered orout-of-network covered user equipments. On the other hand, a D2D device(first UE) sends first signaling to another D2D device (second UE), sothat a format of the D2D discovery signal may be limited and unified, soas to adjust transmission among multiple UEs, reducing mutual conflictand interference in a D2D discovery process and improving transmissionefficiency.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram of a communications system according to anembodiment of the present disclosure;

FIG. 2 is a schematic diagram of another communications system accordingto an embodiment of the present disclosure;

FIG. 3 is a schematic flowchart of a D2D communication method accordingto an embodiment of the present disclosure;

FIG. 4 is a schematic diagram of a D2D link according to an embodimentof the present disclosure;

FIG. 5 is a schematic diagram of another D2D link according to anembodiment of the present disclosure;

FIG. 6 is a schematic diagram of still another D2D link according to anembodiment of the present disclosure;

FIG. 7 is a schematic diagram of carrying first signaling by using aDMRS according to an embodiment of the present disclosure;

FIG. 8 is a schematic structural diagram of UE according to anembodiment of the present disclosure; and

FIG. 9 is a schematic structural diagram of another UE according to anembodiment of the present disclosure.

DESCRIPTION OF EMBODIMENTS

The following describes the technical solutions in the embodiments ofthe present disclosure with reference to the accompanying drawings inthe embodiments of the present disclosure. Apparently, the describedembodiments are merely a part rather than all of the embodiments of thepresent disclosure. The following descriptions are intended forexplanation rather than limitation, and some specific details are statedfor clear understanding. In some embodiments, detailed descriptions ofcommon apparatuses, circuits, and methods are omitted, to avoid makingdescriptions blurry because of unnecessary details. In entiredescriptions, same reference numbers and same names refer to same orsimilar elements.

FIG. 1 and FIG. 2 show, in a form of a schematic diagram, scenarioenvironments to which the embodiments of the present disclosure may beapplied. A scenario includes a cellular communication mode in which abase station is used as a scheduling core and user equipment is used asa scheduled object and also includes a D2D communication mode in whichuser equipments directly communicate with each other. In the cellularcommunication mode, a user equipment (UE) communicates with another UEby means of a base station in a conventional manner. In the D2Dcommunication mode, UEs directly communicate with each other. No mutualforwarding of multi-hop D2D data or signaling exists between D2D UEs inFIG. 1. Mutual forwarding of multi-hop D2D data or signaling may existbetween D2D UEs in FIG. 2.

The D2D communication modes shown in FIG. 1 and FIG. 2 both have twodifferent application scenarios. Left parts in FIG. 1 and FIG. 2 showthe D2D communication mode with partial network coverage, that is, apart (for example, UE 1) of UEs performing D2D communication is withincoverage of a base station in a cellular network, and another part (forexample, UE 2 and UE 3) of the UEs performing D2D communication isbeyond the coverage of the base station. The UE (such as the UE 1)within the coverage of the base station may establish a wirelessconnection to the base station and may also be referred to as in-networkUE. The UE beyond the coverage of the base station may also be referredto as out-of-network UE. It can be understood that there may be one ormore in-network UEs, and there may be one or more out-of-network UEs.Right parts in FIG. 1 and FIG. 2 show the D2D communication mode of ascenario without network coverage, that is, all UEs (for example, UE 4and UE 5) performing D2D communication are all located beyond thecoverage of the base station.

In a scenario shown in FIG. 1, the UE 1 is located within the coverageof the base station and can establish a wireless connection to the basestation. Therefore, the UE 1 is located within a network. UE 2, UE 3, UE4, UE 5, UE 6, UE 7, UE 8, UE 9, and UE 10 are located beyond thecoverage of the base station. Therefore, these UEs are located outsidethe network. It should be noted that in the scenario shown in FIG. 1,although a mutual wireless connection may be established between the UE4, the UE 5, the UE 6, the UE 7, and the UE 8 in a form of, for example,an ad hoc network, because the base station in the cellular network doesnot participate, that is, the UEs are located beyond the coverage of thebase station, these UEs are still considered to be located outside thenetwork.

To more clearly describe the embodiments of the present disclosure,words such as “first”, “second”, and “third” are used in this text todistinguish same or similar items having basically same functions andeffects. A person skilled in the art can understand that words such as“first”, “second”, and “third” do not limit a quantity and an executionsequence. In the D2D communication mode, a D2D device may also bereferred to as D2D UE or UE. First UE, second UE, and third UE in thistext are relative concepts. The D2D device may be used as both a receiveend in a D2D link and a transmit end in another D2D link.

The embodiments of the present disclosure provide a D2D communicationmethod, a D2D device, and a communications system. Solutions provided inthe embodiments of the present disclosure may be applied to D2Dcommunication in a scenario based on a 3GPP LTE system (for example, thescenarios shown in FIG. 1 and FIG. 2), and may be also applied to D2Dcommunication based on another communications system and D2Dcommunication based on a subsequent evolved system.

FIG. 3 is a schematic flowchart of a D2D communication method. A methodprocess includes the following steps.

S302: A D2D device (for example, first UE) determines to-be-sent firstsignaling. The first signaling may be used for D2D discovery.

For example, the first UE may determine the first signaling by itselfaccording to preconfigured information. Alternatively, the first UE maydetermine the first signaling according to information obtained from abase station or another D2D device. In an example, the first UE mayreceive first signaling sent by another D2D device (such as third UE)and determine, according to the received first signaling, the to-be-sentfirst signaling of the first UE. In this case, the first UE isequivalent to performing relay transmission. In another example, thebase station may configure the first signaling of the first UE and sendthe configured first signaling to the first UE.

The to-be-sent first signaling of the first UE, the first signaling sentby the another D2D device (such as the third UE), or the first signalingconfigured by the base station may include one or a combination of thefollowing signaling: a transmission probability, a quantity ofretransmission times, a transmission period, a type of a cyclic prefix(CP), a transmit power, a current quantity of hops, a quantity ofantenna ports, a transmission mode, a bandwidth of a D2D link, a D2Dlink frame number, time division duplexing (TDD) uplink and downlinkconfiguration information, or information indicating whether the firstUE is within a network.

In a specific implementation process, a standard for sending a D2Ddiscovery signal is coordinated and unified between UEs by using firstsignaling, to provide a reference standard for subsequent sending of aD2D discovery signal between UEs, so as to improve a success probabilityof D2D discovery in a D2D discovery process.

S304: The first UE sends the first signaling to second UE. For example,the first UE may send the first signaling to the second UE by using adedicated control channel or a non-control channel in a D2D link.

Specifically, in this embodiment of the present disclosure, a D2D device(the first UE) may send first signaling to another D2D device (thesecond UE), and the first signaling may include any one or more piecesof information of the listed information. For example, the firstsignaling includes the transmission probability. Alternatively, thefirst signaling includes the transmission probability, the quantity ofretransmission times, the transmission period, and the like. This is notspecifically limited in this embodiment of the present disclosure. Theforegoing listed information is briefly described separately below.

Transmission Probability

D2D discovery is divided into a type 1 and a type 2. The type 1 refersto that a transmission resource used by UE serving as a transmit end isconfigured to a group of UEs in a predefined or preconfigured resourcepool during D2D discovery. Each UE selects a transmission resource ofthe UE in the resource pool. The type 2 refers to that a transmissionresource used by UE serving as a transmit end is configured by a networkeach time during D2D discovery. The network herein may be a networkdevice such as a base station. When this embodiment of the presentdisclosure is used for D2D discovery of the type 1, the UE serving as atransmit end, that is, the first UE, randomly selects a transmissionresource in the predefined or preconfigured resource pool according to aparticular transmission probability Pb, or may carry information about atransmission probability Pb in the first signaling sent to UE serving asa receive end, that is, the second UE.

For example, in a partial coverage scenario shown in the left parts ofFIG. 1 and FIG. 2, in-network UE 1 may send the transmission probabilityPb to out-of-network UE 2 and UE 3. Out-of-network UEs such as the UE 2and the UE 3 may randomly select a transmission resource on acorresponding resource by using the transmission probability Pb sent bythe UE 1, so as to send, according to the transmission resource obtainedby random selection, a D2D discovery signal of the transmissionresource. That the in-network UE sends the transmission probability tothe out-of-network UE is equivalent to that the in-network UE controls ause intensity of a resource of the out-of-network UE (for example, agreater probability indicates a higher use intensity of the resource),to ensure that the in-network and out-of-network UEs have a samediscovery opportunity during mutual discovery, facilitating mutualdiscovery of the in-network and out-of-network UEs.

For example, in a scenario without network coverage shown in the rightparts of FIG. 1 and FIG. 2, out-of-network UE 4 may send thetransmission probability Pb to out-of-network UE 5 and UE 6.Out-of-network UEs such as the UE 5 and the UE 6 may randomly select atransmission resource on a corresponding resource by using thetransmission probability Pb sent by the UE 4, so as to send, accordingto the obtained transmission resource, a D2D discovery signal of thetransmission resource. That is, that the out-of-network first UE sendsthe transmission probability to the out-of-network second UE isequivalent to that the out-of-network first UE controls a use intensityof a resource of the out-of-network second UE (for example, a greaterprobability indicates a higher use intensity of the resource), to ensurethat the out-of-network UEs have a same discovery opportunity duringmutual discovery, facilitating mutual discovery of the out-of-networkUEs.

It can be understood that to reduce a quantity of bits occupied by thetransmission probability Pb in the first signaling, the transmissionprobability Pb may be quantized by using limited bits. For example, twobits are used to indicate Pb, and Pb may be quantized into the followingfour values: {0.25, 0.50, 0.75, 1}.

Quantity of Retransmission Times

Similar to the transmission probability, the first UE may carryinformation about the quantity of retransmission times in the firstsignaling sent to the second UE, to instruct the second UE to receive orsend data according to the quantity of retransmission times. Forexample, when the first UE sends a D2D discovery signal, the first UEsends the D2D discovery signal of the first UE according to a particularquantity of retransmission times. The second UE needs to receive,according to the quantity of retransmission times indicated by the firstUE in the first signaling, the D2D discovery signal sent by the firstUE, or otherwise, possibly cannot correctly receive the D2D discoverysignal sent by the first UE. For another example, when the second UE isused as relay UE and starts to send the D2D discovery signal of thesecond UE outwards, the second UE may also send the D2D discovery signalaccording to the quantity of retransmission times indicated in the firstsignaling received by the second UE. In this way, it can be ensured thatUE receiving the D2D discovery signal can also receive, according to thequantity of retransmission times, the D2D discovery signal sent by thesecond UE.

In a specific implementation process, a retransmitted data packet inmultiple times of retransmission may be a same version of a same datapacket or may be different versions that carry same information but thatuse different frequencies, coding schemes, modulation schemes, ortransmission rates.

It can be understood that for different quantities of retransmissiontimes, a quantity of bits as few as possible may be used for indicationto save signaling overheads. For example, two bits are used to indicatethe quantity of retransmission times, and the quantity of retransmissiontimes may be quantized into the following four values: {1, 2, 3, 4}.Certainly, it can be understood that indication may be performed byusing one or more bits. This is not specifically limited in thisembodiment of the present disclosure.

Transmission Period

Because the D2D discovery signal is a discovery signal of a specificformat of a D2D device, sending of the D2D discovery signal may have aparticular delay. Considering that a greater delay can support parallelsending by more users, a transmission period of a D2D discovery signalmay be defined. Within the transmission period, one D2D discovery signalis sent only once. If a transmission period of the D2D discovery signalis properly prolonged, an effect on power consumption brought by the D2Ddevice due to the sending of the D2D discovery signal may also bereduced. Similar to the quantity of retransmission times, thetransmission period may be carried in the first signaling sent by theD2D device.

It can be understood that to reduce a quantity of bits occupied by adiscovery period in the first signaling, the discovery period may bequantized by using limited bits. For example, three bits are used toindicate the discovery period. The discovery period may be quantizedinto the following six values: {32, 64, 128, 256, 512, 1024}. A unit ofthe discovery period may be a radio frame (for example, each radio frameoccupies duration of 10 ms) or a radio subframe (for example, each radiosubframe occupies duration of 1 ms). This is not specifically limited inthis embodiment of the present disclosure.

CP Type

The CP type includes a long CP or a short CP. A quantity of samplingpoints occupied by the long CP is relatively large. For example, usingparameters of a Long Term Evolution (LTE) system as an example, aquantity of sampling points corresponding to a 20 MHz bandwidth is 512,and a corresponding time length is 16.7 μs. A quantity of samplingpoints occupied by the short CP is relatively small. For example, usingparameters of an LTE system as an example, a quantity of sampling pointscorresponding to a 20 MHz bandwidth is 160 (corresponding to a firstOrthogonal Frequency Division Multiplexing (OFDM) symbol on eachsubframe) or 144 (corresponding to a symbol other than a first OFDMsymbol on each subframe), and a corresponding time length is separately5.2 μs or 4.7 μs.

For example, the first UE may carry indication information in the firstsignaling sent to the second UE to indicate the CP type of the first UE.The second UE receives the first signaling, and can know the CP type.Therefore, the second UE does not need to perform blind detectionaccording to different CP types, so as to lower receiving complexity. Inaddition, in a D2D discovery group, mutual interference caused bymultiple UEs due to use of different CP types may be avoided.

It can be understood that because the CP type includes two statuses, thelong CP and the short CP, one bit may be preferably used for indication,so as to reduce signaling overheads. Certainly, it can be understoodthat indication may also be performed by using multiple bits. This isnot specifically limited in this embodiment of the present disclosure.

Transmit Power

The first UE may carry information about the transmit power in the firstsignaling sent to the second UE. For the transmit power of the D2Ddiscovery signal, if the transmit power is excessively large,unnecessary interference may be caused. If the transmit power isexcessively small, coverage of the D2D discovery signal may be affected.For example, the transmit power may be a current transmit power, amaximum transmit power, a minimum transmit power, or a transmit powerthreshold interval. This is not specifically limited in this embodimentof the present disclosure.

It can be understood that the second UE may use the transmit powerindicated in the first signaling sent by the first UE. The second UE mayalso determine the transmit power. A value of the transmit powerdetermined by the second UE satisfies a requirement of the transmitpower indicated by the first UE, for example, is not greater than themaximum transmit power, is not less than the minimum transmit power, oris located within the transmit power threshold interval.

For example, in the scenario of partial coverage shown in the left partsof FIG. 1 and FIG. 2, the in-network UE 1 may indicate to theout-of-network UE 2 and UE 3 the transmit power, for example, thecurrent transmit power, the maximum transmit power, the minimum transmitpower, or the transmit power threshold interval. Therefore, the first UEmay control the transmit powers or transmit power ranges of theout-of-network UE 2 and UE 3, so as to ensure quality of the D2Ddiscovery signal and avoid or lower potential interference between thefirst UE and another in-network UE.

For example, in the scenario without network coverage shown in the rightparts of FIG. 1 and FIG. 2, the out-of-network UE 4 may indicate to theout-of-network UE 5 and UE 6 the transmit power, for example, thecurrent transmit power, the maximum transmit power, the minimum transmitpower, or the transmit power threshold interval. Therefore, the UE 4 maycontrol a transmit power or a transmit power range within a specificout-of-network D2D discovery group, so as to avoid or lower potentialinterference between different out-of-network D2D discovery groups undera condition that coverage is ensured.

It can be understood that to reduce a quantity of bits occupied by thetransmit power in the first signaling, the transmit power may bequantized by using limited bits. For example, two bits are used toindicate the transmit power, and the transmit power may be quantizedinto the following four values: {10, 16, 23, 31} dBm. A value into whichthe transmit power is specifically quantized depends on an upper limitvalue and a lower limit value of a maximum transmit power value that isfinally supported by the system.

Current Quantity of Hops

The current quantity of hops is used to indicate a current quantity ofhops when D2D data is forwarded or a current quantity of hops when theD2D synchronization signal is received. When multi-hop D2D data orsignaling is allowed to be forwarded, coverage of a D2D discovery signalgroup may be expanded, and transmit powers of the UEs are not increased.

For example, when a D2D synchronization signal of particular UE isregularly forwarded by multiple intermediate UEs, UE at a receive endmay determine synchronous source selection according to informationabout a current quantity of hops sent by the intermediate UEs.

For example, when D2D data is forwarded for multiple times, the secondUE may receive data packets of same UE that are forwarded by multiplefirst UEs. In this case, the second UE may determine, according to theinformation about the current quantity of hops sent by the multiplefirst UEs, to receive a data packet sent by first UE. Alternatively, theinformation about the current quantity of hops sent by the multiplefirst UEs may provide a reference indication to a combination of thedata packets sent by the multiple first UEs.

It should be noted that information about a combination of the currentquantity of hops and a maximum quantity of forwarding hops can limit aquantity of times for which D2D data or signaling is allowed to beforwarded, so that the coverage of the D2D discovery signal may becontrolled within a proper range.

It can be understood that to reduce a quantity of bits occupied by thecurrent quantity of hops in the first signaling, the current quantity ofhops may be quantized by using limited bits. For example, if a maximumallowed quantity of hops is defined (indicated by signaling orpreconfigured) as 3, two bits may be used to indicate the currentquantity of hops.

Quantity of Antenna Ports

In the D2D communication mode, the first UE may carry information aboutthe quantity of antenna ports in the first signaling sent to the secondUE, so that the second UE receives or sends data according to theinformation about the quantity of antenna ports.

For example, when the quantity of antenna ports is 1, it indicates thata single antenna mode is currently used by the first UE.Correspondingly, the second UE receives data in the single antenna mode.For another example, when the quantity of antenna ports is 2, itindicates that a multiple-input multiple-output (MIMO) mode is currentlyused by the first UE. In an example, the first UE may also indicate, byusing the first signaling or another signaling, a MIMO mode that thefirst UE specifically uses currently. For example, a MIMO mode that isspecifically used is indicated by using signaling in a MIMO transmissionmode. Detailed description is not provided herein in this embodiment ofthe present disclosure.

It can be understood that one or more bits may be used to indicate thequantity of antenna ports. For example, to reduce a quantity of bitsoccupied by the quantity of antenna ports in the first signaling, thequantity of antenna ports may be quantized by using bits as few aspossible. For example, two bits are used to indicate the quantity ofantenna ports, and the quantity of antenna ports may be quantized intothe following four values: {1, 2, 4, 8}.

Transmission Mode

The transmission mode is used to distinguish various specifictransmission manners. Different transmission manners correspond todifferent structures of transmitters and receivers and also correspondto different transmission effects. Specifically, the transmission modeprovided in this embodiment of the present disclosure may include atleast one of the following transmission modes:

a nonlinear transmission mode or a MIMO transmission mode.

The nonlinear transmission mode is a mode other than linear transmissionmodes such as the MIMO transmission mode and includes non-orthogonalnonlinear transmission modes, such as single-user superimposed codingand multi-user non-orthogonal transmission. The single-user superimposedcoding is specific to single UE and may be that the first UEsuperimposes different data symbols on a same transmission resource withdifferent powers and sends the data symbols to the second UE.Alternatively, the first UE superimposes, with different powers,codewords obtained after different data packets are coded and then sendsthe codewords to the second UE on a same transmission resource. Thesecond UE may separately demodulate on a same transmission resource byusing a method such as serial-parallel interference cancellation toobtain two different pieces of data. The multi-user non-orthogonaltransmission is specific to multiple UEs. When data of two first UEs arenot orthogonal in resources (time, frequencies, codewords, or space),data is simultaneously sent to multiple second UEs. For example, whentwo first UEs are not orthogonal in space, data may be sent to differentsecond UEs by using same or partially same time frequency resources.Different second UEs may first demodulate to obtain a signal of thefirst UE with a greater power and then demodulate to obtain a weakersignal of the first UE according to a serial interference cancellationmethod. In summary, any nonlinear transmission mode is characterized bytransmitting multiple pieces of data on a same resource, so as todrastically improve transmission efficiency. In addition, nonlineartransmission is not limited to multiple antennas, that is, UE with asingle antenna may also use nonlinear transmission.

The MIMO transmission mode includes transmit diversity or spatialmultiplexing. The transmit diversity includes: a Space Frequency BlockCode (SFBC) mode, a Space Time Block Code (STBC) mode, a large-delayCyclic Delay Diversity (CDD) mode, and the like. The spatialmultiplexing is transmitting multiple pieces of data on a same timefrequency resource by using a space domain resource, and needs toindicate information including a quantity of codewords (such as a singlecodeword and double codewords), a quantity of space layers (such asLayer 1, Layer 2, Layer 3, and Layer 4), or the like. Different MIMOmodes support different application scenarios. Generally, the transmitdiversity can improve robustness of a radio link, and can improve anequivalent received signal-to-noise ratio of the second UE under a sametransmit power. The spatial multiplexing can improve transmissionefficiency of per unit time frequency resource under a same transmitpower, that is, a single time frequency resource can transmit more data.The first UE may select a proper MIMO transmission mode according to aneed of current transmission (a need of improving reliability ofcoverage or a link or a need of improving transmission efficiency).

It should be noted that the MIMO spatial multiplexing is usuallyorthogonal or approximately orthogonal in space. In addition, a receiveralso uses a linear equalization receiver to receive and demodulate data.This is a key difference with nonlinear transmission.

It can be understood that one or more bits may be used to indicate thetransmission mode. For example, to reduce a quantity of bits occupied bythe transmission mode in the first signaling, the transmission mode maybe quantized by using bits as few as possible. For example, two bits areused to indicate a quantity of space layers and separately correspond toLayers {1, 2, 3, 4}. Two bits are used to indicate a mode of thetransmit diversity and separately correspond to {SFBC, STBC, CDD}.

Bandwidth of D2D Link

The bandwidth of the D2D link is used to indicate a maximum bandwidthwhen sending is performed on the D2D link.

If the first UE indicates the bandwidth of the D2D link in the firstsignaling sent to the second UE, the second UE may receive and transmitthe D2D discovery signal only within a frequency domain range indicatedby the bandwidth of the D2D link, so as to limit a range of a bandwidthof sending and receiving on the D2D, so that different UEs receive andtransmit data on a specified bandwidth, to facilitate mutual discoverybetween devices.

It can be understood that to reduce a quantity of bits occupied by thebandwidth of the D2D link in the first signaling, the bandwidth of theD2D link may be quantized by using limited bits. For example, sixstatuses of three bits are used to indicate the bandwidth of the D2Dlink, and the bandwidth of the D2D link may be quantized into {6, 15,25, 75, 100} physical resource blocks (PRBs).

D2D Link Frame Number

In D2D communication, UE at a transmit end may carry information aboutthe D2D link frame number in the first signaling sent to UE at a receiveend. The D2D link frame number is used to unify relative timingreference relationships between UEs within a group, so that receivingand transmission of UEs are aligned on a time domain. The transmissionperiod of the D2D discovery signal has actual meanings and effects dueto existence of the information about the D2D link frame number. The D2Dlink frame number may specifically be a radio subframe number and aframe index of the D2D link. This is not specifically limited in thisembodiment of the present disclosure.

It can be understood that to reduce a quantity of bits occupied by theD2D link frame number in the first signaling, the D2D link frame numbermay be quantized by using limited bits. For example, ten bits may beused to indicate serial numbers of {0, 1, . . . , 1023}, 1024 radioframes in total.

TDD Uplink and Downlink Configuration Information

In D2D communication, UE at a transmit end may carry the TDD uplink anddownlink configuration information in the first signaling sent to UE ata receive end. The information is used to indicate a configuration ratioof uplink subframes to downlink subframes in a TDD system. Theconfiguration ratio is used to indicate subframes that are used foruplink transmission and subframes that are used for downlinktransmission under different configurations. If subframes used foruplink transmission are incorrectly used for downlink transmission,mutual communication cannot be implemented, and interference betweenreceiving and transmission links between different TDD UEs is caused.Table 1 is a list of TDD uplink and downlink configuration informationin an LTE system. D represents a downlink subframe, U represents anuplink subframe, and S represents a switching subframe from downlink touplink.

TABLE 1 TDD Switching uplink and point period downlink fromconfiguration downlink to Subframe number information uplink 0 1 2 3 4 56 7 8 9 0  5 ms D S U U U D S U U U 1  5 ms D S U U D D S U U D 2  5 msD S U D D D S U D D 3 10 ms D S U U U D D D D D 4 10 ms D S U U D D D DD D 5 10 ms D S U D D D D D D D 6  5 ms D S U U U D S U U D

It should be noted that currently, the TDD uplink and downlinkconfiguration information in the LTE system has seven statuses shown inTable 1. The seven statuses may be indicated by using three bits.

Information Indicating Whether the First UE is within a Network

UE at a transmit end may carry, in the first signaling sent to UE at areceive end, the information indicating whether the first UE is within anetwork. The information is used to indicate whether the UE at thetransmit end is within a network or is covered by a base station.

For example, in a scenario of partial coverage shown in the left partsof FIG. 1 and FIG. 2, the in-network UE 1 may send to the out-of-networkUE 2 and UE 3 the information indicating whether the first UE is withina network. Out-of-network UEs such as the UE 2 and the UE 3 maydetermine, by using the information that indicates whether the first UEis within a network and that is sent by the UE 1, whether the D2Ddiscovery signal sent by the UE 1 is from the in-network UE, so thatwhen the out-of-network UEs such as the UE 2 and the UE 3 receivemultiple different pieces of indication information, it may beconsidered that data is preferentially received and transmittedaccording to the information indicated by the in-network UE, so as toensure mutual discovery of in-network and out-of-network UEs.

It can be understood that because the information indicating whether thefirst UE is within a network includes two statuses, yes and no,preferably, one bit may be used for indication, so as to reducesignaling overheads. Certainly, it can be understood that indication mayalso be performed by using multiple bits. This is not specificallylimited in this embodiment of the present disclosure.

It should be noted that information that may be included in the firstsignaling is briefly described above. Certainly, the first signaling mayfurther include another information other than the foregoing listedinformation. This is not specifically limited in this embodiment of thepresent disclosure.

Optionally, one item of information or a combination of multiple itemsof information in the first signaling may be used to implicitly indicateinformation not included in the first signaling. For example, anassociation relationship between information that may be included in thefirst signaling may be established. The first signaling may include onlyone or more items in the association relationship, and UE used for D2Dcommunication can know another item in the association relationshipaccording to the first signaling and the association relationship.

In an example, an association relationship between the transmissionprobability and the bandwidth of the D2D link may be established. Whenthe UE used for D2D communication knows one of the transmissionprobability or the bandwidth of the D2D link, the UE may know the otheritem of information according to the association relationship. Forexample, as shown in Table 2, if the transmission probability includedin the first signaling is 1, it may be implicitly indicated that thebandwidth of the D2D link is 6 PRB. Alternatively, if the bandwidth ofthe D2D link included in the first signaling is 6 PRB, it may beimplicitly indicated that the transmission probability is 1.

TABLE 2 Bandwidth value (PRB) Transmission probability value 6 1 15 0.7525 0.5 50 0.5 75 0.25 100 0.25

In another example, similarly, an association relationship between thequantity of retransmission times and the transmit power of the D2Ddiscovery signal may be established. When the UE used for D2Dcommunication knows one of the transmission probability or the bandwidthof the D2D link in the D2D discovery signal, the UE may know the otheritem of information according to the association relationship. As shownin Table 3, by means of the association relationship, or for example, ifthe quantity of retransmission times included in the first signaling is1, it may be indicated according to the quantity of retransmission timesthat the transmit power is 10 dBm. Alternatively, if the transmit powerincluded in the first signaling is 10 dBm, it may be indicated accordingto the transmit power that the quantity of retransmission times is 1.

TABLE 3 Quantity of retransmission times Transmit power (dBm) 1 10 2 163 23 4 31

In an example, a D2D device (the first UE) may receive the firstsignaling sent by another D2D device (the third UE), and receive or senddata according to the first signaling. The first UE may also transmitthe D2D synchronization signal in the D2D link. For example, in FIG. 3,the second UE receives the first signaling from the first UE or mayreceive or send data according to the first signaling, or receive orsend the synchronization signal.

It should be noted that when the first UE performs relay transmission,the first signaling transmitted in UEs with different quantities offorwarding hops may be same or different. For example, when the first UEforwards the first signaling, the first UE may modify the informationabout the quantity of hops in the first signaling. Situations regardingthat when the D2D data or the D2D synchronization signal has one or morehops, the first UE sends the first signaling to the second UE by usingthe D2D link are provided below.

Situation 1

FIG. 4 shows a multi-hop scenario of the D2D communication mode. In thescenario shown in FIG. 4, the D2D synchronization signal has multiplehops, and the D2D data has only one hop. In FIG. 4, a solid line is usedto represent D2D synchronization signal transmission, and a dashed lineis used to represent D2D data transmission.

As shown in FIG. 4, data of the UEs is transmitted only between two UEsand is not forwarded by the UE at the receive end. Therefore, the D2Ddata has only one hop. For example, data of the UE 1 is transmitted onlybetween the UE 1 and the UE 5 or between the UE 1 and the UE 2.Therefore, UEs can only be mutually discovered. For example, the UE 2can discover the UE 3, the UE 1, and the UE 5, but cannot discover theUE 6 or the UE 4.

In the scenario shown in FIG. 4, the D2D synchronization signal may betransmitted between multiple UEs, and all UEs may use the same D2Dsynchronization signal. Only quantities of forwarding hops of the D2Dsynchronization signal are different. For example, assuming that the UE1 is first UE that sends the D2D synchronization signal, a currentquantity of hops at which the first UE is located is 0. The UE 2 and theUE 5 separately receive the D2D synchronization signal of the UE 1 andsynchronize with the UE 1. In this case, the quantity of hops of the D2Dsynchronization signal of the UE 2 and the UE 5 is 1. The UE 2 and theUE 5 separately send the D2D synchronization signal to the UE 3 and theUE 6. In this case, the quantity of hops of the D2D synchronizationsignal of the UE 3 is 2. Similarly, the quantity of hops of thesynchronization signal of the UE 4 is 3. Assuming that a maximumquantity of hops of the D2D synchronization signal is 3, forwarding ofthe D2D synchronization signal ends at the UE 4, that is, the UE 4 doesnot send the D2D synchronization signal outwards according to timing ofthe UE 1.

In an example of the present disclosure, the first signaling isforwarded only between UEs sending the D2D synchronization signal. Whenforwarding the first signaling, the UE needs to update the informationabout the current quantity of hops in the first signaling.

In an example, all UEs in FIG. 4 are considered to be within a D2Ddiscovery group. Although D2D data of the UEs has only one hop, bysending the first signaling, mutual interference within the group canstill be controlled, and a corresponding transmission resource can becoordinated.

Situation 2

FIG. 5 shows another multi-hop scenario of the D2D communication mode.In the scenario shown in FIG. 5, the D2D synchronization signal and theD2D data both have multiple hops. In FIG. 5, a solid line is used torepresent D2D synchronization signal transmission, and a dashed line isused to represent D2D data transmission.

In the scenario shown in FIG. 5, there are two possible sending mannersto send the first signaling. Manner 1: One of the UE sending the D2Ddata or the UE sending the D2D synchronization signal sends or forwardsthe first signaling. Manner 2: The UE sending the D2D data and the UEsending the D2D synchronization signal separately send the firstsignaling. The sent first signaling may be the same or different. In themanner 2, because mechanisms of sending the D2D data or the D2Dsynchronization signal by different UEs may be different, and theforwarded current quantities of hops may also be different, fields inthe first signaling sent by the different UEs may be configuredindependent of each other. This is not specifically limited in thisembodiment of the present disclosure.

In the scenario shown in FIG. 5, because D2D data of the UEs can beforwarded, the UEs are not limited to being only capable of mutuallydiscovering two corresponding parties of D2D communication. For example,the UE 2 can discover the UE 3, the UE 1, and the UE 5. In addition,because the UE 2 forwards data of the UE 1 to the UE 3, the UE 3 canalso discover the UE 1. Similarly, the UE 3 further forwards the data ofthe UE 1 to the UE 4, and the UE 4 can also discover the UE 1.Similarly, the UE 6 can also discover the UE 1 by means of forwarding bythe UE 5. In view of the above, in this embodiment, coverage of D2Ddiscovery may be expanded by forwarding the D2D data.

Situation 3

FIG. 6 shows still another multi-hop scenario of the D2D communicationmode. In this scenario, the D2D synchronization signal has only one hop,but the D2D data has multiple hops. A thick dashed line represents aquantity of hops forwarded by the D2D synchronization signal, and a thindashed line represents a quantity of hops forwarded by the D2D data. UE7 provides coverage of a one-hop D2D synchronization signal to all UEsin FIG. 6. In this scenario, the UE 7 providing the D2D synchronizationsignal may have a larger transmit power and greater coverage.

In the scenario shown in FIG. 6, the first signaling may be forwardedbetween UEs sending the D2D data. When forwarding the first signaling,different UEs sending the D2D data may update the information about thecurrent quantity of hops in the first signaling. For example, a quantityof hops of the UE 1 is 0, a quantity of hops of the UE 2 is 1, and aquantity of hops of the UE 3 is 2. If a predefined maximum quantity ofhops is 3, the UE 4 does not forward the D2D data of the UE 1 outwardsany longer.

It should be noted that in the foregoing three situations, the UEsending the D2D data and the UE sending the D2D synchronization signalmay perform relay transmission. The UE sending the D2D data and the UEsending the D2D synchronization signal may be same UE or may bededicated UEs separately providing the D2D synchronization signal. Thisis not specifically limited in this embodiment of the presentdisclosure.

In a specific implementation process, optionally, the D2Dsynchronization signal may be used to indicate a channel carrying thefirst signaling in the D2D link. The D2D synchronization signal includesa primary sidelink synchronization signal (PSSS) and a secondarysidelink synchronization signal (SSSS). Sidelink synchronization signalidentities (SLSSID) that correspond to the PSSS and the SSSS areintegers not less than 336, and the SLSSIDs are used to identify achannel carrying the first signaling in the D2D link.

In an example, the SLSSID in the prior art may be used. The SLSSID isindicated to the UE receiving the D2D synchronization signal after theUE sending the D2D synchronization signal maps the SLSSIDs to the D2Dsynchronization signals one by one. Table 4 shows an example of anSLSSID mapping relationship. There are two sequences for generating thePSSS, corresponding root sequence numbers v are respectively 26 and 37,and corresponding identities PSSIDs are 0 and 1. There are 168 secondarysynchronization sequences for generating the SSSS, a correspondingidentity SSSSID is [0, 167], a value range of the SLSSIDs correspondingto the PSSS and the SSSS is [0, 335], and one D2D synchronization signaluniquely corresponds to one SLSSID.

TABLE 4 PSSS root sequence number v PSSSID SSSSID SLSSID 26 0 [0, 167] [0, 167] 37 1 [0, 167] [168, 335]

In another example, the SLSSID of the D2D link is modified by increasinga quantity of the PSSSs or SSSSs. For example:

Table 5 shows another example of an SLSSID mapping relationship list.Compared with the example shown in Table 4, the SSSS remains the same(that is, the value of the SSSSID is still [0, 167]), and the PSSS isexpanded (for example, a PSSS is added). The SLSSIDs that correspond tothe PSSS and the SSSS are separately mapped to [336, 503] one by one.

TABLE 5 PSSS root sequence number v PSSSID SSSSID SLSSID v2 2 [0, 167][336, 503]

It should be noted that the root sequence number v2 corresponding to thesequence for generating the PSSS is a sequence number different fromexisting root sequence numbers 26 and 37. For example, the root sequencenumber v2 may be one of the following values: 22, 23, 40, or 41.Certainly, more root sequences v may be used to expand the PSSSsequence, so as to expand available SLSSIDs. This is not specificallylimited in this embodiment of the present disclosure.

Table 6 shows still another example of an SLSSID mapping relationshiplist. Compared with the example shown in Table 4, the PSSS remains thesame, and the SSSS is expanded (for example, a new SSSS is added). TheSLSSIDs that correspond to the PSSS and the SSSS are separately mappedto [336, 671] one by one.

TABLE 6 PSSS root sequence number u PSSSID SSSSID SLSSID 26 0 [168, 335][336, 503] 37 1 [168, 335] [504, 671]

It can be understood that ranges of the expanded SSSS and the SSSSIDcorresponding to the SSSS may not be limited to values provided in Table6. This is not specifically limited in this embodiment of the presentdisclosure.

Because generation of a scrambling sequence and a demodulation referencesignal (DMRS) sequence of a dedicated control channel carrying the firstsignaling is related to the SLSSIDs, the dedicated control channelcarrying the first signaling in this embodiment of the presentdisclosure may be distinguished or uniquely identified by separatelymapping the SLSSIDs of the D2D link to integers not less than 336 one byone.

In an example, in the foregoing S304, the first UE may send the firstsignaling to the second UE by using a dedicated control channel in theD2D link.

In D2D characteristics of the 3rd Generation Partnership Project (3GPP)protocol release (Rel) 12, a physical sidelink broadcast channel (PSBCH)is defined. In an example of the present disclosure, a reserved field inan existing PSBCH channel may be used, to carry the first signaling.This is equivalent to defining a new dedicated control channel. That is,the dedicated control channel includes the reserved field, and some orall bits in the reserved field are used to carry the first signaling.For example, some of bits in the existing PSBCH channel are used asreserved fields, and a total quantity of bits of the reserved fields is27. Therefore, some or all bits in these reserved fields may be used toindicate the first signaling. For example, four bits are used toseparately indicate the quantity of retransmission times (such as twobits) and the transmission probability (such as two bits). Positions ofthe four bits may be the front, the middle, or the end of the reservedfield. This is not specifically limited in this embodiment of thepresent disclosure.

In another example of the present disclosure, the dedicated controlchannel may also be a channel that uses a time frequency resourcedifferent from that of the PSBCH or a channel in which carried contentand/or a transmission manner is different from that of the PSBCH. Thisis not limited in the present disclosure.

In a specific implementation process, that the dedicated control channelis used to carry the first signaling may be identified in multiplemanners.

In a possible implementation, the dedicated control channel may furthercarry second signaling, and the second signaling is used to identifythat the dedicated control channel is a channel carrying the firstsignaling.

For example, when the first signaling is transmitted in an independentdedicated control channel, the second signaling may be carried in thededicated control channel. The second signaling is used to identify thatthe dedicated control channel is a channel carrying the first signaling.Preferably, the second signaling may be indicated by using one bit. Theone bit may be a bit in an actual status, for example, one added bit.When a value of the bit is 1, it represents that the dedicated controlchannel is the dedicated control channel carrying the first signaling.Otherwise, the dedicated control channel is not the dedicated controlchannel carrying the first signaling. Alternatively, the one bit doesnot have any actual physical meaning and may not be filled with a valueor be filled with only a fixed value (such as 0 or 1), to achieve anobjective of making a length of the dedicated control channel carryingthe first signaling not equal to a length of the PSBCH defined in theD2D characteristics of the 3GPP protocol Rel-12.

In a possible implementation, the dedicated control channel may carry aDMRS, the DMRS is used to identify that the dedicated control channel isa channel carrying the first signaling, and a generation parameter ucorresponding to the DMRS satisfies:

u=(f _(gh)(n _(s))+f _(ss))mod 30+b, where

n_(s) is a non-negative integer and represents a timeslot number or asubframe number, f_(gh)(n_(s)) is an integer and represents a sequencegroup hop, f_(ss) is an integer and represents a sequence hop, modrepresents a modulo operation, and b is a non-zero integer.

Specifically, in the prior art, when a root sequence of the DMRS of thePSBCH defined in the D2D characteristics of the 3GPP protocol Rel-12 isselected, a mechanism is the same as that in LTE, and only the sequencegroup hop and the sequence hop of a DMRS generation sequence are closed.

For the parameter u=(f_(gh)(n_(s))+f_(ss)) mod 30 generating the DMRS,when the sequence group hop is closed, f_(gh)(n_(s))=0. When thesequence hop is closed, f_(ss)=SLSSID mod 30.

In this implementation of this embodiment of the present disclosure, inthe parameter u=(f_(gh)(n_(s))+f_(ss)) mod 30+b generating the DMRS, bis a non-zero integer.

Alternatively, if the sequence group hop is not closed, f_(gh)(n_(s))≠0.

Alternatively, if the sequence hop is not closed, f_(ss)=((SLSSID mod30)+Δ) mod 30.

In this way, a generated DMRS carried by the dedicated control channelis different from a generated DMRS carried by the PSBCH channel, so thatthe dedicated control channel is different from the PSBCH defined in theD2D characteristics of the 3GPP protocol Rel-12.

Further, f_(ss) in the generation parameter u=(f_(gh)(n_(s))+f_(ss)) mod30 corresponding to the DMRS satisfies: f_(ss)=((SLSSID mod 30)+Δ) mod30, where

the SLSSID is an integer not less than 0, and Δ is a non-zero constant.

That is, the SLSSID may be an SLSSID (that is, [0, 335]) in an existingD2D link or may be a remapped SLSSID (that is, an integer not less than336) in the D2D link in the foregoing embodiment. This is notspecifically limited in this embodiment of the present disclosure.

In a possible implementation, the dedicated control channel is scrambledby using a scrambling sequence when being generated, the scramblingsequence is used to identify that the dedicated control channel is achannel carrying the first signaling, and an initial value c_(init) usedwhen the scrambling sequence is generated satisfies:

c _(init) =nSLSSID or c _(init) =n _(RNTI)*2¹⁴ +q*2¹³ +└n_(s)/2┘*2⁹+SLSSID, where

n_(RNTI), q, and n_(s) are all non-zero integers, SLSSID is an integernot less than 0, and nSLSSID is an integer not less than 336.

That is, the SLSSID may be an SLSSID (that is, [0, 335]) in an existingD2D link or may be a remapped SLSSID (that is, an integer not less than336) in the D2D link in the foregoing embodiment. This is notspecifically limited in this embodiment of the present disclosure. ThenSLSSID is a remapped SLSSID (that is, an integer not less than 336) inthe D2D link in the foregoing embodiment.

Specifically, in the PSBCH defined in the D2D characteristics of theexisting 3GPP protocol Rel-12, an initial value formula when thescrambling sequence is generated is: c_(init)=SLSSID, where SLSSID is aninteger between [0, 335]. In this embodiment of the present disclosure,in the dedicated control channel carrying the first signaling, theinitial value formula c_(init) when the scrambling sequence is generatedsatisfies: c_(init)=nSLSSID, orc_(init)=n_(RNTI)*2¹⁴+q*2¹³+└n_(s)/2┘*2⁹+SLSSID, where nSLSSID is aninteger not less than 336. Therefore, the initial value of thescrambling sequence used when the dedicated control channel carrying thefirst signaling is generated is different from an initial value of ascrambling sequence used when the PSBCH defined in the D2Dcharacteristics of the 3GPP protocol Rel-12 is generated, so that thededicated control channel carrying the first signaling is different fromthe PSBCH defined in the D2D characteristics of the 3GPP protocolRel-12.

In a possible implementation, the dedicated control channel uses acyclic redundancy check (CRC) mask when being generated, and the CRCmask is used to identify that the dedicated control channel is a channelcarrying the first signaling.

Specifically, in the PSBCH defined in the D2D characteristics of theexisting 3GPP protocol Rel-12, 16-bit CRC is used, and a CRC mask is notused, or a default CRC mask is all 0. The CRC mask refers to adding apredefined bit sequence of 0 and 1 that has a length the same as a CRClength to a CRC field after coding. If there is no CRC mask, duringdecoding, CRC is directly performed on an information bit obtained bydecoding. If a CRC result is correct, a whole process of receiving,demodulation, and decoding of this data packet is considered to becorrect. Otherwise, the process is considered to be incorrect.

If the CRC mask is added to CRC, before CRC is performed, the CRC maskneeds to be removed first, and then CRC is performed. In this way, anobtained result is an expected check result. Otherwise, CRC is basicallyincorrect. In this embodiment of the present disclosure, when beinggenerated, the dedicated control channel uses the CRC mask, and the CRCmask is used to identify that the dedicated control channel is a channelcarrying the first signaling. That is, whether the channel is the PSBCHdefined in the D2D characteristics of the 3GPP protocol Rel-12 or thededicated control channel carrying the first signaling may bedistinguished by using the CRC mask.

For example, a bit string with a length of 16 bits, for example,1111111111111111, 1100110011001100, or 10011001100110011001, may be usedas the CRC mask. It can be understood that it is feasible as long as theCRC mask is not an all-0 bit string. Bit strings are not listed one byone herein in this embodiment of the present disclosure.

In another example, in the foregoing S304, the first UE may also sendthe first signaling to the second UE by using a non-control channel inthe D2D link. For example, the first signaling may be carried in one ora combination of the following manners: the CRC mask, the D2Dsynchronization signal, or the DMRS. This is described in detail below.

(a) CRC Mask

Specifically, using an LTE system as an example, the D2D discoverysignal occupies two physical resource blocks (PRBs). A data packet has afixed size and includes 24-bit CRC, 232 bits in total. The firstsignaling may be carried by using the CRC mask. For example, 2-bitinformation in the first signaling may be carried by using fourdifferent CRC masks. For another example, 3-bit information in the firstsignaling may be carried by using eight different CRC masks.

Table 7 provides an example of a mapping relationship between a 24-bitCRC mask and an information status in the first signaling. It is assumedthat the information status is of two bits. For example, the quantity ofretransmission times is indicated by using two bits. If the CRC mask is111100001111000011110000, it can be known from Table 7 that the firstsignaling carried by the CRC mask indicates that the quantity ofretransmission times is 3 (the corresponding 2-bit information status is10).

TABLE 7 24-bit CRC mask Information status 000011110000111100001111 00000000000000111111111111 01 111100001111000011110000 10111111111111000000000000 11

It should be noted that a mapping relationship between a CRC mask and aninformation status in the first signaling is provided only as anexample. Certainly, other mapping relationships may also exist. Themapping relationships are not listed one by one herein in thisembodiment of the present disclosure.

(b) D2D Synchronization Signal

Specifically, when the first signaling is carried by the D2Dsynchronization signal, different sequences of the D2D synchronizationsignal are divided into M subgroups, and the M subgroups are used tocarry information not exceeding n=floor(log₂ (M) bits, where a floorfunction represents rounding down to the nearest integer.

For example, assuming that 168 sequences of the D2D synchronizationsignal are divided into eight subgroups in total, 3-bit information inthe first signaling may be carried by using the D2D synchronizationsignal, and each subgroup includes 21 sequences. A grouping method maybe numbering one by one starting from sequences, as shown in Table 8.

It is assumed that the corresponding information status is of threebits. An information status of two lower bits corresponds to thequantity of retransmission times, and an information status of one upperbit corresponds to information indicating whether the first UE is withina network. When the information indicating whether the first UE iswithin a network is “1”, it indicates that the first UE is within anetwork. When the information indicating whether the first UE is withina network is “0”, it indicates that the first UE is out of a network. Ifa sequence index of the D2D synchronization signal is 45, it can beknown from Table 8 that the first signaling carried by the D2Dsynchronization information indicates that the quantity ofretransmission times is 3 (two corresponding lower bits on the right are10), and the first UE is out of a network (a corresponding highest biton the left is 0).

TABLE 8 Sequence index of D2D synchronization signal Information status 0-20 000 21-41 001 42-62 010 63-83 011  84-104 100 105-125 101 126-146110 147-167 111

It should be noted that a grouping mapping relationship betweendifferent sequences of the D2D synchronization signal is provided onlyas an example. Certainly, other grouping mapping relationships may alsoexist. The mapping relationships are not listed one by one herein inthis embodiment of the present disclosure.

(c) DMRS

Specifically, using an LTE system as an example, the D2D discoverysignal occupies two PRBs, and a corresponding length on a frequencydomain is of 24 subcarriers, and a length of a corresponding DMRS is 24.When the first signaling is carried by the DMRS, the first signaling iscarried by cyclic shifts of different DMRSs in the D2D link.Alternatively, the first signaling is carried by a modulation symbol oneither of two neighboring DMRSs in the D2D link. Alternatively, thefirst signaling is carried by modulation symbols on two neighboringDMRSs in the D2D link.

The foregoing three manners of carrying, by the DMRS, the firstsignaling are briefly described below separately.

Manner 1: The first signaling is carried by cyclic shifts of differentDMRSs in the D2D link.

Specifically, the cyclic shift is generated by rotating a sequencecorresponding to the DMRS used on a frequency domain by one phase, asfollows:

r ^((α))(n)=e ^(jαn) r(n),0≤n<M, where

α represents a phase value corresponding to the cyclic shift, r(n)represents a sequence before the cyclic shift, and a length of thesequence is M.

For example, the DMRS may have eight different cyclic shift values andcorrespond to a 3-bit status, and may be used to carry 3-bit informationin the first signaling. Different cyclic shift values correspond todifferent information statuses and are not listed one by one herein.

Manner 2: The first signaling is carried by a modulation symbol oneither of two neighboring DMRSs in the D2D link.

Specifically, an interval between two neighboring DMRSs in a time domainis 0.5 ms. A modulation symbol may be sent on one of two neighboringDMRSs, so that the modulation symbol carries the first signaling. Forexample, a quaternary phase shift keying (QPSK) symbol can indicate2-bit information. A 16 quadrature amplitude modulation (QAM) symbol canindicate 4-bit information. A 64 QAM symbol can indicate 6-bitinformation.

As shown in FIG. 11, FIG. 11 shows a DMRS that is of a D2D discoverysignal and that is used to transmit a modulation symbol. The modulationsymbol may be mapped to any one of neighboring DMRSs in a subframe, anda modulation may be performed in a direct spreading manner. That is,assuming that DMRS representation chips in a timeslot n are: d1, d2, . .. , and dL, and a to-be-modulated QAM symbol is x, the DMRS chips in thetimeslot n after symbol modulation become: d1*x, d2*x, . . . , and dL*x.

Manner 3: The first signaling is carried by modulation symbols on twoneighboring DMRSs in the D2D link.

In FIG. 11, assuming that DMRS representation chips in a timeslot n are:d1, d2, . . . , and dL, and a to-be-modulated QAM symbol is x, thesymbol x may also be simultaneously placed on different chips of twoneighboring DMRSs. For example, the symbol x is placed on differentchips of the timeslot n and a timeslot n+1 at equal intervals. Thetimeslot n is: d1, d2*x, d3, d4*x, . . . , d(L−1), and dL*x.

The timeslot n+1 is: d1*x, d2, d3*x, d4, . . . , d(L−1)*x, and dL.

It should be noted that in the foregoing manner 2 and manner 3, afterreceiving the first signaling sent by the first UE, the second UE maydemodulate, by using two neighboring DMRSs, the symbol that carries xafter modulation. This is not specifically limited in this embodiment ofthe present disclosure.

It should be noted that the carrying manner of the non-control channelis only briefly described above. Certainly, in addition to the foregoinglisted carrying manner of the non-control channel, other carryingmanners of the non-control channel may exist. In addition, a singlecarrying manner of the non-control channel is only provided above.Certainly, there may also be a combination of multiple carrying mannersof the non-control channel, such as carrying of the CRC mask andcarrying of the D2D synchronization signal. This is not specificallylimited in this embodiment of the present disclosure.

It can be understood that carrying the first signaling by using thenon-control channel may not increase extra system overheads. Therefore,system resources are saved.

Optionally, the first UE shown in FIG. 3 may be in-network UE, and thefirst UE satisfies at least one of a condition A or a condition B:

Condition A: Quality of a signal that is received by the first UE andthat is from the base station is less than a first threshold.

Condition B: Quality of a signal that is received by the first UE andthat is from out-of-network UE is greater than a second threshold.

When the first UE detects that the UE satisfies the condition A, itindicates that the first UE is at an edge position of a coverage area ofthe base station. In this case, the first UE may limit some userequipments to forward the first signaling of the first UE, so as tolimit a quantity of participating UEs and improve signaling transmissionefficiency.

When the first UE detects that the UE satisfies the condition B, itindicates that the first UE detects an out-of-network D2D signal, andthe first UE may trigger to send the first signaling according to thisevent.

When the first UE detects that the UE satisfies both the condition A andthe condition B, the UE is triggered to send the first signaling, and aquantity of UEs forwarding the first signaling is limited, so as toensure that only a few or specific UEs send the first signaling andserve the out-of-network UE as much as possible.

The quality of the signal that is received by the first UE and that isfrom the out-of-network UE in the condition B may be signal quality ofthe D2D discovery signal that is detected by the first UE and that isfrom the out-of-network UE, or may be signal quality of the D2Dsynchronization signal that is detected by the first UE and that is fromthe out-of-network UE; and/or the quality of the signal that is receivedby the first UE and that is from the out-of-network UE in the conditionB may be signal quality of a reference signal that is on anout-of-network D2D control channel and/or a control channel and that ismeasured by the first UE; and/or the quality of the signal that isreceived by the first UE and that is from the out-of-network UE in thecondition B may be signal quality of a reference signal that is on adata packet of the D2D discovery signal and/or the D2D discovery signaland that is measured by the first UE. This is not specifically limitedin this embodiment of the present disclosure.

The foregoing determining condition may be not only applicable to ascenario in which the first UE has a radio resource control (RRC)connection but also applicable to a scenario in which the first UE hasno RRC connection.

Optionally, the first UE shown in FIG. 3 may also be out-of-network UE,and the first UE satisfies a condition C: Condition C: quality of asignal that is received by the first UE and that is from another UE isless than a third threshold.

The quality of the signal that is received by the first UE and that isfrom another UE in the condition C may be signal quality of the D2Ddiscovery signal that is detected by the first UE and that is from thein-network or out-of-network UE, or may be signal quality of the D2Dsynchronization signal that is detected by the first UE and that is fromthe out-of-network UE; and/or the quality of the signal that is receivedby the first UE and that is from another UE in the condition C may besignal quality of a reference signal that is on an out-of-network D2Dcontrol channel and/or a control channel and that is measured by thefirst UE; and/or the quality of the signal that is received by the firstUE and that is from another UE in the condition C may be signal qualityof a reference signal that is on a data packet of the D2D discoverysignal and/or the D2D discovery signal from the in-network orout-of-network UE and that is detected by the first UE. This is notspecifically limited in this embodiment of the present disclosure.

It should be noted that the condition C is applicable to a scenario ofno network. In this case, if the first UE detects that signal strengthof another UE is less than the third threshold, it indicates thatnecessary coverage of the D2D signal lacks around the first UE.Therefore, the first UE may send D2D related signaling, including thefirst signaling in this embodiment of the present disclosure.

The signal quality may include: a reference signal received power(RSRP), received signal strength indication (RSSI), reference signalreceived quality (RSRQ), a signal to interference plus noise ratio(SINR), and the like. This is not specifically limited in thisembodiment of the present disclosure.

The first threshold, the second threshold, or the third threshold may bepredefined or may be configured for the first UE by a network by usingsignaling. This is not specifically limited in this embodiment of thepresent disclosure.

In an example, the first signaling not only may be used for D2Ddiscovery but also may be used for D2D communication. Functions ofparameters when the first signaling is used for D2D communication arebriefly described below.

Information such as the bandwidth of the D2D link, the D2D link framenumber, the TDD uplink and downlink configuration information, andinformation indicating whether the first UE is within a network isinformation necessary for indicating D2D communication and isinformation that needs to be mutually confirmed to implement datatransmission between the transmitter and the receiver in a D2Dcommunication process.

Information about the quantity of antenna ports and the transmissionmode is signaling that is necessarily indicated after nonlineartransmission and MIMO transmission are introduced into D2Dcommunication. Otherwise, multi-antenna and nonlinear transmissioncannot be supported.

The current quantity of hops refers to information that needs to beindicated when relay transmission supporting multiple hops is introducedbetween D2D communication devices. With information about the currentquantity of hops, when a data packet from UE is forwarded to the secondUE by different first UEs at different quantities of hops, the second UEmay select to receive the data packet or combine the data packetaccording to the information about the current quantity of hops.

Information such as the transmission probability, the quantity ofretransmission times, the transmission period, the CP type, and thetransmit power may be used to optimize transmission of D2Dcommunication, for example, controlling use intensity of resources,reducing a quantity of blind detection times, and reducing unnecessaryinterference between multiple groups of users.

When the first signaling is used for D2D communication, the firstsignaling may be used to enhance D2D communication. For example, atleast one of the following aspects may be enhanced: Nonlineartransmission and multi-antenna MIMO transmission are introduced byindicating information about the quantity of antenna ports and thetransmission mode; a configurable mechanism of the quantity ofretransmission times is introduced by indicating information about thequantity of retransmission times; control over use intensity ofresources is optimized by indicating information about the transmissionprobability; transmit powers of nodes are optimized by indicatinginformation about the transmit power; D2D communication is expanded to arelay mode supporting multiple hops by indicating information about thecurrent quantity of hops; or blind detection of the receiver is reducedby indicating the CP type, so as to reduce unnecessary calculation andpower consumption.

When the first signaling is used for D2D communication, refer to thesignaling transmission method in the foregoing D2D discovery process fora signaling transmission method. The transmission methods are notdescribed herein in this embodiment of the present disclosure.

In the solution provided in this embodiment of the present disclosure, aD2D device (such as first UE) sends first signaling to another D2Ddevice (such as second UE) by using a D2D link, so that different D2Ddevices can receive and transmit data by using same parameters in a sameresource pool (a set of user resources) when sending a D2D discoverysignal, so as to implement D2D discovery between partially covered orout-of-network covered user equipments. On the other hand, a D2D device(such as the first UE) sends first signaling to another D2D device (suchas the second UE), so that a format of the D2D discovery signal may belimited and unified, so as to adjust transmission among multiple UEs,reducing mutual conflict and interference in a D2D discovery process andimproving transmission efficiency.

An embodiment of the present disclosure further provides a userequipment (UE), including corresponding modules configured to performbehaviors of the first UE in the foregoing method designs. The modulesmay be software and/or hardware.

FIG. 8 shows a design block diagram of a user equipment (UE) involved inthe foregoing embodiments. The UE 80 may be used as the first UE or thesecond UE in the foregoing embodiments. The UE 80 includes: a processingunit 81 and a communications unit 82. The processing unit 81 isconfigured to control and manage actions of the UE and is configured toperform processing performed by the first UE or the second UE in theforegoing embodiments. For example, the processing unit 81 is configuredto determine first signaling used for D2D discovery. The communicationsunit 82 is configured to support communication between the UE 80 andanother network element. For example, the communications unit 82 isconfigured to communicate with another UE or a base station and sendand/or receive data. Refer to description in the foregoing embodimentsfor the first signaling and the actions of the UE. The first signalingand the actions of the UE are not described herein.

FIG. 9 shows another design block diagram of a user equipment (UE)involved in the foregoing embodiments.

An encoder 906 receives service data and a signaling message to be senton an uplink. The encoder 906 processes (for example, formatting,encoding, and interleaving) the service data and the signaling message.A modulator 907 further processes (for example, symbol mapping andmodulation) the encoded service data and signaling message and providesoutput sampling. A transmitter 901 adjusts (for example, analogconversion, filtering, amplification, and up-conversion) the outputsampling and generates an uplink signal or a D2D link signal. The uplinksignal is transmitted to the base station or the D2D device (such as thesecond UE) in the foregoing embodiments by using an antenna. The antennareceives a downlink signal transmitted by the base station and a D2Dlink signal from another D2D device in the foregoing embodiments. Areceiver 902 adjusts (for example, filtering, amplification,down-conversion, and digitization) a signal received from the antennaand provides input sampling. A demodulator 909 processes (for example,demodulation) the input sampling and provides symbol estimation. Adecoder 908 processes (for example, de-interleaving and decoding) thesymbol estimation and provides the decoded data and signaling messagesent to the UE. The encoder 906, the modulator 907, the demodulator 909,and the decoder 908 may be implemented by a modem processor 905. Theseunits perform processing according to a radio access technology (forexample, LTE and access technologies of other evolved systems, such as aD2D communication technology) used by a radio access network.

A controller/processor 903 controls and manages the actions of the UEand is configured to perform processing performed by the UE in theforegoing embodiments. For example, the controller/processor 903 isconfigured to control the UE to determine to-be-sent first signalingand/or another process of a technology described in the presentdisclosure. In an example, the controller/processor 903 is configured tosupport the UE to perform the processes S302 and S304 in FIG. 3. Amemory 904 is configured to store program code and data used for the UE.

The controller/processor for performing functions of the UE in thepresent disclosure may be a central processing unit (CPU), a generalpurpose processor, a digital signal processor (DSP), anapplication-specific integrated circuit (ASIC), a field programmablegate array (FPGA) or another programmable logic device, a transistorlogic device, a hardware component, or any combination thereof. Thecontroller/processor can implement or perform various examples of logicblocks, modules, and circuits described with reference to contentdisclosed in the present disclosure. The processor may also be acombination that implements a calculation function, for example,including one microprocessor or a combination of multiplemicroprocessors, or a combination of a DSP and a microprocessor.

Steps of the method or algorithm described with reference to contentdisclosed in the present disclosure may be directly embodied ashardware, software modules executed by the processor, or a combinationof the hardware and the software modules. The software modules may belocated in a RAM memory, a flash memory, a ROM memory, an EPROM memory,an EEPROM memory, a register, a hard disk, a removable hard disk, aCD-ROM or a storage medium of any other form well known in the art. Anexample of a storage medium is coupled to the processor, so that theprocessor can read information from the storage medium and can writeinformation to the storage medium. Certainly, the storage medium mayalso be a component of the processor. The processor and the storagemedium may be located in an ASIC. In addition, the ASIC may be locatedin the user equipment. Certainly, the processor and the storage mediummay also exist in the user equipment as discrete components.

A person skilled in the art should realize that in the foregoing one ormore examples, functions described in the present disclosure can beimplemented by hardware, software, firmware, or any combination thereof.When the present disclosure is implemented by software, the foregoingfunctions may be stored in a computer-readable medium or transmitted asone or more instructions or code in the computer-readable medium. Thecomputer-readable medium includes a computer storage medium and acommunications medium, where the communications medium includes anymedium that enables a computer program to be transmitted from one placeto another. The storage medium may be any available medium accessible toa general-purpose or dedicated computer.

The foregoing descriptions are merely specific implementations of thepresent disclosure, but are not intended to limit the protection scopeof the present disclosure. Any variation or replacement readily figuredout by a person skilled in the art within the technical scope disclosedin the present disclosure shall fall within the protection scope of thepresent disclosure. Therefore, the protection scope of the presentdisclosure shall be subject to the protection scope of the claims.

What is claimed is:
 1. A device to device (D2D) communication method,the method comprising: determining, by a first D2D device, firstsignaling to be sent, wherein the first signaling comprises one or acombination of the following information: a transmission period, aquantity of antenna ports, a Multiple-Input Multiple-Output (MIMO)transmission mode, time division duplexing (TDD) uplink and downlinkconfiguration information, or information indicating whether the firstD2D device is within a network; and sending, by the first D2D device,the first signaling to a second D2D device using a dedicated controlchannel in the D2D link; wherein the dedicated control channel isscrambled by using a scrambling sequence when being generated, whereinthe scrambling sequence is used to identify that the dedicated controlchannel is a channel carrying the first signaling, and an initial valuec_(init) used when the scrambling sequence is generated is an integernot less than
 336. 2. The method according to claim 1, wherein thedetermining, by the first D2D device, the first signaling comprises:determining, by the first D2D device, the first signaling according topreconfigured information; or receiving, by the first D2D device, asignaling from a third D2D device using the D2D link, and determiningthe first signaling according to the signaling received from the thirdD2D device; or receiving, by the first D2D device, a signaling from abase station, and determining the first signaling according to thesignaling received from the base station.
 3. The method according toclaim 1, wherein the information comprised in the first signaling isfurther used to implicitly indicate second information comprised in thefirst signaling.
 4. The method according to claim 1, further comprising:transmitting, by the first D2D device, a D2D synchronization signal inthe D2D link, wherein the D2D synchronization signal comprises a primarysidelink synchronization signal (PSSS) and a secondary sidelinksynchronization signal (SSSS), wherein sidelink synchronization signalidentities (SLSSIDs) that correspond to the PSSS and the SSSS areintegers not less than 336, and the SLSSIDs are used to identify achannel carrying the first signaling in the D2D link.
 5. The methodaccording to claim 1, wherein the dedicated control channel comprises areserved field, and some or all bits in the reserved field are used tocarry the first signaling.
 6. The method according to claim 1, whereinthe dedicated control channel further carries second signaling, and thesecond signaling is used to identify that the dedicated control channelis a channel carrying the first signaling.
 7. The method according toclaim 1, wherein the dedicated control channel uses a cyclic redundancycheck (CRC) mask when being generated, and the CRC mask is used toidentify that the dedicated control channel is a channel carrying thefirst signaling.
 8. The method according to claim 1, wherein thesending, by the first D2D device, the first signaling to the second D2Ddevice using the D2D link comprises: sending, by the first D2D device,the first signaling to the second D2D device using the D2D link, whereinthe first signaling is carried in one or a combination of the followingmanners: a cyclic redundancy check (CRC) mask, a D2D synchronizationsignal, or a demodulation reference signal (DMRS).
 9. The methodaccording to claim 1, wherein the initial value used when the scramblingsequence is generated is a value c_(init) that satisfies:c_(init)=nSLSSID, wherein nSLSSID is an integer not less than
 336. 10. Adevice to device (D2D) device for D2D communication, the D2D devicecomprising: a processor; and a transmitter, wherein the processor isconfigured to determine first signaling to be sent, wherein the firstsignaling comprises one or a combination of the following information: atransmission period, a quantity of antenna ports, a Multiple-InputMultiple-Output (MIMO) transmission mode, a D2D link frame number, timedivision duplexing (TDD) uplink and downlink configuration information,or information indicating whether the D2D device is within a network;wherein the transmitter is configured to send the first signaling tosecond D2D device using a dedicated control channel in the D2D link; andwherein the dedicated control channel is scrambled by using a scramblingsequence when being generated, wherein the scrambling sequence is usedto identify that the dedicated control channel is a channel carrying thefirst signaling, and an initial value used when the scrambling sequenceis generated is an integer not less than
 336. 11. The D2D deviceaccording to claim 10, further comprising a receiver, wherein: theprocessor is configured to determine the first signaling according topreconfigured information; or the receiver is configured to receivesignaling from a third D2D device using the D2D link, and the processoris configured to determine the first signaling according to thesignaling that is received from the third D2D device and that isreceived by the receiver; or the receiver is configured to receivesignaling from a base station, and the processor is configured todetermine the first signaling according to the signaling received fromthe base station and that is received by the receiver.
 12. The D2Ddevice according to claim 10, wherein the information comprised in thefirst signaling is further used to implicitly indicate secondinformation comprised in the first signaling.
 13. The D2D deviceaccording to claim 10, wherein the transmitter is further configured totransmit a D2D synchronization signal in the D2D link, wherein the D2Dsynchronization signal comprises a primary sidelink synchronizationsignal (PSSS) and a secondary sidelink synchronization signal (SSSS),wherein sidelink synchronization signal identities (SLSSIDs) thatcorrespond to the PSSS and the SSSS are integers not less than 336, andthe SLSSIDs are used to identify a channel carrying the first signalingin the D2D link.
 14. The D2D device according to claim 10, wherein thededicated control channel further carries second signaling, and thesecond signaling is used to identify that the dedicated control channelis a channel carrying the first signaling.
 15. The D2D device accordingto claim 10, wherein the dedicated control channel uses a cyclicredundancy check (CRC) mask when being generated, and the CRC mask isused to identify that the dedicated control channel is a channelcarrying the first signaling.
 16. The D2D device according to claim 10,wherein the first signaling is carried in one or a combination of thefollowing manners: a cyclic redundancy check (CRC) mask, a D2Dsynchronization signal, or a demodulation reference signal (DMRS). 17.The D2D device according to claim 10, wherein the initial value usedwhen the scrambling sequence is generated is a value c_(init) thatsatisfies: c_(init)=nSLSSID, wherein nSLSSID is an integer not less than336.